As of July 29, 2013, LinkedIn Signal will no longer be available. After this date, you will no longer be able to search status updates or access any of your saved Signal searches. Until then, you can access Signal from the Search page, by clicking the Update Type link on the left side of the page.
Why is LinkedIn doing this?
The LinkedIn team is continually working on developing more useful products and features for members like you. This sometimes means we will incorporate a feature into another product or remove it completely. Although this feature will no longer be available, you'll still be able to search for people, companies, keywords and jobs you are interested in directly from your LinkedIn homepage using the search bar.